Animal litter composition

ABSTRACT

An animal litter mixture comprising pine wood and silica gel is provided. The pinewood is preferably a sawdust form, although the pinewood may be in the form of fine shavings or compressed pellets. The silica gel may have one porosity or a mixture of porosity. In one embodiment of the animal litter mixture, the silica gel may be an indicator gel that changes colors when the silica is saturated with water.

This application is a continuation application of U.S. application Ser.No. 11/261,253, filed on 28 Oct. 2005, which application claims thebenefit of U.S. Provisional Application 60/622,870 filed on 28 Oct.2004, which provisional application is herein incorporated by reference.

BACKGROUND OF THE INVENTION

The present invention relates to animal litter and, more particularly,compositions for animal litter and methods of making animal litter.

Many different types of absorbant substances are used as animal litterincluding recycled newspaper, paper sludge, wheat, soybeans, ground corncob granules, rice hulls, peanut hulls, sunflower hulls, cedar, sawdustand other organic materials. Clay, however, is the most common form ofanimal litter, e.g., used as cat litter, on the market making up to 80%to 90% of the litter market.

Clay based litter is available in either sand-like clumping ornon-clumping gravel-like forms. Clumping clay litter contains sodiumbentonite, a particularly absorbant type of clay (a gelling clay) whichforms clumps after contacting animal urine and then can be scooped outof the litter pan to reduce odor from urine. More litter must be addedto replace the litter that was thrown away. Advantageously, not all thelitter has to be thrown away at the same time, and therefore it iseconomical, as less litter is needed.

In comparison, non-clumping litter does not form clumps when in contactwith urine. The solid feces must be picked out and thrown away regularlybut, at some point, the entire litter must be thrown out as urineaccumulates at the bottom of the pan and the odor becomes objectionableover time. Because urine collects at the bottom of the pan, non-clumpingclay litter does not last as long compared to clumping clay litter andnon-clumping clay litter becomes objectionable more quickly, as itcannot be scooped out.

Clay-based animal litters present several disadvantages. Clays containsilica (silicon dioxide) dust that may be harmful to the health ofanimals, e.g., felines, and humans when inhaled. Prolonged inhalation ofsilica dust, which contains crystalline silica, can lead to silicosis, arespiratory disease caused by the inhalation of silica dust, which cancause scar formation within lung tissue and can obstruct the flow ofoxygen into the lungs and bloodstream.

When clumping clay is used, the clumps formed by absorption of urinemust be thrown out daily, in addition to removing the solid feces in thelitter. The clumps may fall apart during removal and thus require someadditional effort. With any clay based litter, odor is oftenobjectionable after only a few days as urine pools at the bottom of thelitter pan and causes the litter to stick to the pan. Use of clay alsohas some other disadvantages. Clay is a non-renewable resource usuallyobtained by stripping land and thus causing scarring of land. The U.S.Bureau of Mines estimates that in 1994, approximately 1.5 million metrictons of clay were mined to make absorbent cat litter and much of it wasstripped mined. Clay is heavy and dense and as a result, lifting alitter pan filled with clay litter can be inconvenient or difficult forsome individuals.

A major problem with clays and most other litter materials is the odorthat is associated with ammonia present in urine. Urine is often coatedover the outer surface of the litter material rather than absorbedwithin the material. As a result, the odor is volatilized into the air.The problem of odor emanating as a by-product of urine and fecal matterhas been dealt with in many ways. Odor masking agents have been used tohide odors. See for example, U.S. Pat. Nos. 4,020,156 to Murray et. atand to U.S. Pat. No. 4,085,704 to Frazier. Both patents are hereinincorporated by reference. Disadvantageously, the methods disclosed inthese patents merely mask but do not eliminate the odor.

Another approach taken is to kill the microorganisms that create odors.This approach is taken in U.S. Pat. Nos. 4,607,594; 4,930443; 4,607,594;5,005,520; and 5,507,205, all of which patents are herein incorporatedby reference.

More recently, silica gel has been used as animal litter. See, forexample, U.S. Pat. No. 5,970,915, which is herein incorporated byreference in its entirety. Silica gel can adsorb its weight in moistureand with some types of silica gel up to twice their weight. Silica geladsorbs moisture from the urine, thereby helping to eliminate the odorproduced by the presence of urine. Advantageously, silica gel may beflushed in small amounts and it will not clog septic systems.

A significant problem, however, with the use of silica gel is itsrelatively high cost compared to other types of litter material. Itshould be emphasized that silica gel does not contain the type ofharmful silica found in clay. Instead, silica gel is an amorphous formthat is essentially chemically inert and relatively non-toxic. Someanimal litters use solely silica gel. Such a purely silica gel animallitter is relatively costly compared to other types of animal litters.

U.S. Pat. No. 6,578,521 to Raymond, et al., was granted for a littercomposition comprising a mixture of absorbant material and silica gel.The '521 patent describes the use of clay and silica gel composition ormixture. A major disadvantage of a clay and silica gel animal litter isthat it still employs clay. Absorbant clay is a non-renewable resource,which is mined, dried and ground to a desirable consistency. Claycontains crystalline silica which is a known carcinogen, according tothe California EPA. Dust controlling agents are often added by themanufacturer to control the dust. Even with dust controlling agentsadded, it is nevertheless dusty and heavy, even at 50% weight of thetotal litter. Regardless of the weight mixture, any combination ofsilica gel and clay will be dusty and will be tracked on the animalsfeed and, moreover, breathing such dust whether silica gel or silicafrom the clay, into animal or human lungs is undesirable.

What is needed is a cat litter that is effective, economical, and yetsafer to humans and animals than clay-based litters.

SUMMARY OF THE INVENTION

In one aspect, an animal litter mixture is provided, the mixturecomprising: silica gel and pinewood. In a preferred embodiment, thepinewood is sawdust, although the pinewood may be other forms such asshavings or compressed pellets made from sawdust.

In one embodiment, the animal litter mixture may have silica gel in themixture that is between 0.5% to 25% by weight of the total animal littermixture. The pine wood material may be chosen from many of the commonpines that are used for the home construction industry, e.g., whitepine, yellow pine, ponderosa pine, sugar pine and white spruce.

In various embodiments of the animal litter mixture, the silica gel maybe a type C silica gel, a type B silica gel or a mixture of both type Band C silica gel. The mixture of type B and C gels can provide differentmoisture adsorption characteristics.

The silica gel used in the animal litter mixtures may have colorindicating characteristics. That is, when the silica gel has adsorbedsufficient water, i.e., becomes saturated, the silica gel turns adifferent color, e.g., blue to purple. A preferred type of indicator gelis an Orange Indicator Silica Gel.

While the sawdust aggregate particle size may range greatly, it ispreferred that the sawdust have a largest dimension of between 1 and 3millimeters. It is noted, however, that sawdust or pinewood particlesize may be larger or smaller and is, regardless of particle size,within the scope of the present invention.

It is a feature of this invention to provide an animal litter that isless costly than 100% silica gel animal litter.

It is another feature of this invention to provide an animal litter thatproduces less dust than a purely clay litter or litter mixture of clayand silica gel;

It is another feature of this invention to provide an animal litter thatis lighter for equivalent volume than a litter that is pure clay or alitter that is a mixture of clay and silica gel or essentially puresilica gel.

It is further a feature to provide an animal litter that is economic toproduce, friendlier to the environment than litter having clay, is lesstoxic than a clay base litter and is safe to a septic system in smallamounts.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows an illustration of a mixture of animal litter based on pinesawdust and silica gel; and

FIG. 2 shows an illustration of a cylindrical shaped wood pellet and aspherical shaped wood pellet.

DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

FIG. 1 shows a representation of animal litter, in accordance with anembodiment of the present invention. In a preferred embodiment, inaccordance with the present invention, the animal litter is acombination mixture of pine wood 10 and silica gel 20. Preferably thepinewood 10 is in a sawdust form. However, the pine wood may also be inform of small wood shavings (not shown) or cylindrical pellets 30 orspherical pellets 40 which have been formed by compressing sawdust.

Silica gel 20 may be manufactured as a porous, amorphous form of silica(SiO₂). Silica gel is very different than other types of silica forms inthat silica gel contains a network of microscopic pores. Silica gels canhave pores having diameter ranges between about 5 Angstroms to about3000 Angstroms. It is possible to produce silica gels in a wide varietyof pore sizes. Common silica gel may have pore sizes ranging from about60 Angstroms to about 125 Angstroms. Type A silica gels can have poresizes that are less than about 20 Angstroms. Type B silica gels havepore sizes that range from about 20 Angstroms to about 100 Angstroms andType C silica gels can have pore sizes that are greater than 100Angstroms. Other ways of categorizing silica gels include “narrow pore”silica gels (average pore size about 20 Angstroms) and “wide pore”(average pore size about 110 Angstroms and greater). “Large pore” silicagel can have pore diameters that range from about 300 Angstroms to about1000 Angstroms.

Narrow pore and wide pore silica can act differently with liquid water.Liquid water can destroy narrow pore silica gels but wide pore silicagels are not affected. Silica gel adsorb moisture due to van der Waalsinteractions and capillary condensation. Certain grades of silica canadsorb up to 1.2 times their own weight in water.

Silica gel can also be made with a Blue Silica Gel which changes colorsdepending on the level of adsorbed water. This type of indicator gel maybe produced by combining Narrow Pore Silica gel (pore diameter: 2-3nanometers with surface area less than or equal to 600 m²/g of gel) withchloride cobalt (CoCl₂). As water is adsorbed, the color of the gelchanges from blue to purple. Another type of silica gel is an OrangeSilica Gel Indicator. The main advantage is that the Orange Silica Gelis believed to be less toxic than the cobalt laden Blue Silica gel.

The use of pine wood for animal litter has been known for many years.For example, pinewood shavings or sawdust, alone, has been used asanimal litter. Wood shavings have been used for a long time as absorbentand odor minimizing bedding material for various animals, includinghamsters, mice, and guinea pigs.

Wood material has been recently used as cat litter. For example, onecompany, Pine Fresh, uses kiln dried recycled pine wood. The advantagestouted is that it is renewable, not toxic to animal or humans, and isrelatively dust free and can be flushed in small amounts into citysewage. Wood as absorbent material may come in at least three forms,ground up sawdust, sawdust formed into pellets, and small wood shavings.The pelletized form can absorb many times its weight in urine and growsin size. U.S. Pat. No. 5,927,049 provides a method of processing yellowpine wood into a pelletized form to be used, by itself, for animallitter. While the pelletized form is compact compared to a sawdust form,the disadvantage of the pelletize form is that it is costlier than theother forms, e.g., shavings, or sawdust since the formation of pelletsrequires additional processing. Pine wood sawdust, such as thoseproduced as waste material from producing lumber for building woods,e.g., two-by-fours, are preferred woods for use as litter material. Pineis relatively low in cost. Pine wood naturally absorbs many times itweight in urine and neutralizes ammonia.

Many different types of pine may be used, in accordance with the presentinvention. Some types of pines that may be used include white pine,yellow pine, ponderosa pine, sugar pine, among others. Pine wood is agood material for use as animal litter because it contains aromatic oilsthat neutralize the ammonia in animal urine, such as highly concentratedcat urine, and can effectively reduce odor. Pine sawdust by itself, whenused, for example with cats, can last approximately two weeks before theodor becomes so strong and offensive that the sawdust must be tossedout.

In accordance with the present invention, it has been discovered that amixture of pine sawdust and silica gel provides results that aresuperior to using pine sawdust or silica gel alone. Surprisingly,combining pine wood with the dessicant properties of silica gel resultsin an improved animal litter that lasts much longer than pine wood byitself. A small amount of silica gel mixed with the pine wood,preferably in sawdust form, can effectively lengthen the useful life ofpinewood litter by at least twice the duration, e.g., about a month oreven more, when used as animal litter such as cat litter. Thecombination pine wood sawdust and silica gel (a) quickly absorbs urine(b) neutralizes odors from urine and fecal waste and (c) can beadvantageously flushed into a septic tank in small amounts or even canbe safely used in compost. The combination pine wood sawdust and silicagel mixture is economical to manufacture since most of the mixture ispine wood sawdust which is relatively inexpensive.

In one embodiment of the present invention, the silica gel used in thepine sawdust silica gel mixture is an indicator gel. It may be possibleto use Blue Silica Gel in some mixtures. More preferably, however, asilica gel having an orange indicator is preferred. It will beunderstood that the concept of using an indicator color incorporatedinto the silica gel to indicate saturation of water within the silicagel, as used in combination with a pine sawdust and silica gel mixture,comes within the scope of the present invention.

The following provides some examples of the combination pine wood andsilica gel animal litter mixtures, in accordance with the presentinvention.

EXAMPLE 1

Type C silica gel mixed with a pine wood sawdust. The silica gelrepresents between about 1 to 25% by weight of the total weight of theanimal litter.

EXAMPLE 2

Same mixture of Example 1 above, except the silica gel incorporates anindicator color, e.g., an Orange Silica Gel.

EXAMPLE 3

Type B and C silica gel, mixed with a pine wood sawdust. The type Bsilica gel makes ups about 50% of the total silica gel weight and thetype C silica gel makes up about 50% of the total silica gel weight. Thetotal silica gel weight is between 5 to 25% by weight of the mixture ofthe total weight of the animal litter.

EXAMPLE 4

Same mixture as Example 3, except that the Type B gel incorporates anindicator color, e.g., an Orange silica gel.

EXAMPLE 5

Same mixture as Example 3, except that the Type C gel incorporates anindicator color, e.g., an Orange silica gel.

EXAMPLE 6

Same as previous examples except using pine wood shavings or compressedpinewood pellets are used, instead of pinewood sawdust. The compressedpellets, of embodiments shown in FIG. 2, can be at least 1 millimeteracross the largest dimension. In this example the pellet may be betweenabout 1 to about 7 millimeters across the largest dimension and may becylindrical 30 or spherical 40 in shape.

Our animal use tests have indicated that the combination is moreeffective than using pine sawdust alone and has better odor neutralizingproperties than pure silica gel. Furthermore, one embodiment of theinvention comprising pine wood (in sawdust form) and silica gel, issuperior to a mixture of absorbant clay and silica gel as taught in U.S.Pat. No. 6,578,521. It is believed that use of dried pinewood provides(1) water absorption and (2) a natural, anti-bacterial agent, whichreduces bacteria produced odor and (3) a natural chemical agent toneutralize urine. In addition, the silica gel provides added wateradsorption into micropores and, moreover, (4) provides a vehicle for awater saturation indicator. In addition, it has been discovered that thepinewood and silica gel, helps control odor better than a pure silicagel litter, a pure clay litter or for that matter, a mixture of clay andsilica gel.

A pine wood and silica gel mixture is further advantageous compared toclay because a mixture of pine wood and silica gel avoids using clay,which contains harmful silica dust. In addition, the pine wood sawdustand silica gel mixture is lighter per volume of animal litter mixturethan a clay-silica gel litter mixture. Avoiding the use of non-renewableabsorbant clay and using a renewable pinewood sawdust is also better forthe environment. In addition, a pinewood and silica gel mixture is lessdusty than an animal litter mixture of pure clay or a mixture of clayand silica gel.

The invention has been described in terms of exemplary embodiments. Theinvention, however, is not limited to the embodiments depicted anddescribed and it is contemplated that other embodiments, which may bereadily devised by persons of ordinary skill in the art, based on theteachings set forth, are within the scope of the invention.

1. An animal litter mixture, comprising: silica gel; and pine sawdust,wherein the silica gel is between 1% to 25% by weight of the animallitter mixture.
 2. The animal litter mixture of claim 1, wherein thesilica gel includes one or more of a B silica gel.
 3. The animal littermixture of claim 1, wherein the pine sawdust is chosen from the groupconsisting of white pine, yellow pine, ponderosa pine, sugar pine andwhite spruce.
 4. The animal litter mixture of claim 1, wherein thesilica gel includes a C silica gel.
 5. The animal litter mixture ofclaim 1, wherein the silica gel includes at least some indicator silicagel that can change color to indicate water saturation.
 6. The animallitter mixture of claim 1, wherein the silica gel has an average porediameter of greater than about 100 Angstroms.
 7. The animal littermixture of claim 6, wherein the silica gel has an average pore diameterthat is between about 100 Angstroms and about 1000 Angstroms.
 8. Theanimal litter mixture of claim 1, wherein the silica gel is a mixture oftype B and type C silica gel; and wherein the type B silica gel hasmedium pores between about 20 to 100 Angstroms and type C silica gel haslarge pores that are greater than 100 Angstroms.
 9. The animal littermixture of claim 8, wherein the silica gel mixture includes at leastsome indicator silica gel for indicating water saturation.
 10. Theanimal litter mixture of claim 9, wherein the indicator silica gel ischosen from the group consisting of an Orange indicator silica gel and aBlue indicator silica gel.
 11. The animal litter mixture of claim 8,wherein the type C silica gel includes at least some indicator silicagel for indicating water saturation.
 12. The animal litter mixture ofclaim 1, wherein the sawdust has a largest dimension of between 0.5 to3.0 millimeters.
 13. An animal litter mixture, comprising: silica gel;pine wood, wherein the pine wood is in the form of compressed pellets;and wherein the silica gel is between 1% to 25% by weight of the animallitter mixture.
 14. The animal litter mixture of claim 13, wherein thepine wood is chosen from the group consisting of white pine, yellowpine, ponderosa pine, sugar pine and white spruce.
 15. The animal littermixture of claim 13, wherein the pellet is shaped as a sphere.
 16. Theanimal litter mixture of claim 13, wherein the silica gel includes atleast some indicator silica gel that changes color to indicate watersaturation.
 17. The animal litter mixture of claim 13, wherein thesilica gel has an average pore diameter of greater than about 100Angstroms.
 18. The animal litter mixture of claim 17, wherein the silicagel has an average pore diameter that is between about 100 Angstroms andabout 1000 Angstroms.
 19. The animal litter mixture of claim 13, whereinthe silica gel is a mixture of type B and type C silica gel; wherein thetype B silica gel has medium pores between about 20 to 100 Angstroms andtype C silica gel has large pores that are greater than 100 Angstroms;and wherein the silica gel includes indicator silica gel for indicatingwater saturation.
 20. The animal litter mixture of claim 13, wherein thecompressed wood is cylindrical in shape.